Featured on TV programs and commercials, miniature pigs are becoming popular pets, but despite increasing numbers of Web sites dedicated to rearing them, owners can be in for a few surprises, not least their tendency to get too big to handle.

Yumiko Murata, 32, of the city of Ageo, Saitama Prefecture, said it was "love at first sight" when she bought her miniature pig, a species originally bred for use in biomedical research, at a pet shop in 2003 for 80,000 yen.

The shop clerk told Murata, who had only kept a hamster before, that she could give it chicken feed. But the minipig developed diarrhea, and four months later she read on the home page of Shigehisa Kobayashi, who wrote a book about how to raise the animals, that the diarrhea was caused by antibiotics in the chicken feed. Special food was needed.